1. Field of the Invention
The present invention relates to an interface control device, an electronic equipment, and a communication system, and more particularly to a communication system for digital data transfer using a serial bus interface, an electronic equipment for digital data transfer using such a system, and a control device for controlling such a system.
2. Related Background Art
With the development of recent multimedia techniques, various types of data in various formats can be transferred via one digital I/F (interface) system under various communication protocols.
There is an equipment capable of using only one communication protocol although it has a plurality of functional units, in which each unit can be externally controlled and can transfer data to and from external devices. One of digital I/F bus systems of this kind is an IEEE 1394 serial bus.
In order to deal with nodes having various functions, the IEEE 1394 serial bus is generally provided with, in addition to a protocol common to IEEE 1394, other different communication protocols. In this specification, a common protocol independent from functional units of each equipment, although it is specific to each serial bus such as IEEE 1394 serial bus, is called a fundamental protocol, whereas a protocol dependent upon each functional unit is called a subsidiary communication protocol.
Specifically, even for digital data communications in conformity with the fundamental protocol of a digital I/F bus system, it is generally necessary that a subsidiary communication protocol defined for each node terminal (I/F terminal) matches the protocol of the communication partner, and the communication partner is required to have means for converting the format of received data into a format usable at the communication partner.
The subsidiary communication protocol is generally standardized in accordance with the genre (category) of each equipment or its unit. Therefore, each node has been generally configured as an equipment compatible with a single subsidiary communication protocol.
Definition (definition of node information) of an equipment as viewed from a digital I/F bus has been difficult to generate if a plurality of functions provided by the equipment cannot be operated at the same time, or if the unit configuration or the subsidiary communication protocol changes because of connecting a new unit or attachment.
Even if an equipment is an image input equipment having only a single function, the input image may be used in a different manner at the communication partner. In such a case, it is desired that subsidiary communication protocols different for each use type such as displaying, recording and printing are separately prepared. It is also necessary to consider that a different subsidiary communication protocol may be used by each manufacture of the equipment, even if both the function and use type are the same.